In a medical setting it may be necessary or desirable to transfer fluid to/from a subject for a variety of reasons. For example, a hub connected to a needle or other cannula may be used to draw blood from a vein or to infuse fluid substances i.e., intravenous (IV) therapy. A drip is one type of IV therapy. IV therapy may be used to correct electrolyte imbalances, to deliver medications or nutrition, for blood transfusion or as fluid replacement to correct dehydration. IV therapy can also be used for chemotherapy of cancer patients. Fluid-transferring devices such as syringes may also be attached to a hub that connects a cannula for the addition or removal of fluid to/from a variety of bodily cavities, organs, or vessels. For instance, the hub may be part of an entity providing a catheter to drain urine from the bladder or kidney, to remove fluid from an abscess, to extract liquid from joints or cysts, or to administer breathing gases through a tracheal tube. A typical endotracheal tube may include a cuff inflation tube with a hub for attachment of a syringe to enable inflation to seal the trachea and bronchial tree against air leakage and aspiration of fluids. A tracheostomy tube or urinary tract catheter might also use a cuff system with a hub for connection of a syringe or other device to inject fluid to inflate a cup or balloon that holds it in place. However fluid injections using a syringe connected to a needle are one of the most common health care procedures in the world.
When transferring fluids to/from a subject, the hub with its needle, catheter or other cannula inserted in the patient is often left in-situ while the fluid-transferring device may be removed and replaced, e.g., to empty/re-fill a syringe or to change over the IV therapy. Where two medical devices that carry small fluid volumes must be connected, a standard Luer fitting is the most common means of achieving a leak-free junction. One type of Luer fitting, commonly called a “Luer lock/lok”, uses an internally threaded collar surrounding a “Luer slip” friction fit (see below) tapered male tip of a syringe or the like. The projecting tip can be inserted into a corresponding female hub with an external thread, or other suitable protrusion for cooperating with the collar, and the collar screwed down on the hub to lock the connection. Such Luer lock fittings have the advantage of providing a secure connection that cannot easily come loose, but two hands are needed to hold the hub while screwing the device in/out. A more rapid form of attachment may be preferred in some circumstances, for example in an emergency situation. Another type of Luer fitting, commonly called a “Luer slip”, simply uses a friction fit between a female hub and corresponding tapered male tip of a device without a threaded collar. A standard friction fit may be achieved by a 6% taper. A Luer slip attachment is common for infusing less viscous fluids, such as vaccinations, and transferring fluids where high pressures are not involved, for example when drawing blood.
A problem observed with both Luer lock and Luer slip connections is the risk of injury when detaching the fluid-transferring device from a hub on a cannula that is still connected to a patient. Although a medical practitioner might take care to hold the hub and avoid injury when unscrewing a Luer lock connection, there is a temptation with a Luer slip connection to try to pull the device from the hub e.g., with one hand. However this can easily result in the hub being tugged away from the body and causing tissue damage. Often the device may not be pulled in a straight line with the cannula connected to the hub, but rotated, and this can twist the components. The tape used to hold the hub e.g., IV port in position is often loosened from the skin and its cannula e.g., needle may even be accidentally extracted. When emptying fluid from a body cavity, for example, keeping the needle hub still when detaching the syringe can be essential to avoid diffuse cutting inside the cavity or damage of the cavity wall. In addition there is a risk of unacknowledged contamination of both the hub and the Luer tip (not only the user) when holding the very small hub with the thumb and index fingers while pulling away the male tip, the tip sliding past the user's fingers as it is released.
Moreover tugging with a single hand does not usually apply enough force even to pull the device out of a friction fitting (such as a Luer slip) and, depending on the force used when connecting the Luer slip tip to the hub, the practitioner usually needs to hold or push the hub while also pulling the device so that it becomes detached. Typically the device will be rotated simultaneously while pulling away from the hub. This jerking can result in unwanted extraction of the needle or other component connected to the hub. The connection will often be pressurised by fluid. For example, a cuff connected to a tracheostomy tube, endotracheal tube or urinary catheter often has a tight connection of the male Luer tip with two-handed operation being required to loosen the connection while the sprung piston in the female Luer hub blocks the outflow of fluid (air or liquid) from the cuff.
Several medical procedures involve targeted introduction of an empty syringe connected to a cannula or other catheter. Such procedures require careful insertion of the cannula or catheter and also careful removal of the syringe if the catheter or cannula is left in situ. The process typically involves applying negative pressure in the syringe by pulling the plunger/piston back during the inward insertion movement of the cannula or catheter towards a target inside the patient. The objective is to verify that the correct target has been reached by drawing a body liquid, e.g., blood, cerebrospinal fluid, synovial fluid from joints, bile, or urine into the syringe barrel where it can be observed. When the appropriate liquid is seen in the barrel, the user can be sure that the catheter tip is in the correct position. Some procedures involve the use of additional guiding tools, e.g., ultrasound guided cannula insertion. During such procedures the user must hold onto the ultrasound probe in addition to the syringe, and monitor the position of the cannula or catheter on a screen. After reaching the target with the tip, the operator typically needs to detach the syringe from the catheter hub. Using conventional methods this can inadvertently cause the tip to dislocate from its intended targeted original position as two handed operation is required to remove the hub. Furthermore during such ultrasound-guided techniques for catheter tip placement, the ultrasound probe is typically put aside/inactivated before the disconnection and therefore the user loses the ability to accurately monitor the position of the tip.
Ease of disconnection can be a problem not only when detaching a device from a hub connected to a patient but also when it is desired to fill/empty a device such as a syringe via a fluid hub in a quick and convenient manner. For example, when filling a syringe using a needle inserted in a vial, each time that the syringe is removed it requires two hands to firmly grasp the needle hub and the syringe to separate them while the needle remains in the vial. As mentioned above, there is again a risk of contamination as the user grasps the hub and the tip comes into contact with the fingers holding the hub.
Another situation where a user might come into contact with a needle hub is when using a blood collection tube. The blood tubes are evacuated plastic or glass containers sealed with an elastomeric septum that is piercable by a double-ended needle to draw venous blood. Due to the piercing force and pressure differential, a secure connection to the needle assembly is required and therefore a threaded Luer lock connection is normally used rather than a Luer slip. U.S. Pat. No. 5,201,716 proposes an alternative blood specimen collection system that does not require the needle assembly to be grasped and twisted during disconnection. In this system a needle assembly is mounted with an interference fit rather than a threaded connection. A pivotally mounted lever assembly is spring-biased to hold the needle assembly in position, i.e., to provide an additional level of security over the friction fit. If the lever is actuated against its spring bias then there is only an interference fit holding the needle assembly in place. The lever can be pivoted to simultaneously release the spring bias and to apply a forward ejection force to the needle assembly.
In any situation where one hand is holding a needle hub while pulling a device away there is a risk of needlestick injury and contamination. Needle caps frequently being mislaid or forgotten can exacerbate this. This also applies when separating a needle or other contaminated component from a syringe or similar device for disposal purposes, with many needlestick injuries occurring when trying to remove sharps to throw into a bin. Usually the person handling a syringe will try to cover a contaminated needle with a cap after use, before grasping the hub to separate the needle from the syringe barrel for disposal. However, when mounting a needle cap onto the contaminated needle a person will use the large muscle groups in the arms and shoulders that work less precisely and, combined with poor depth of vision, this often results in a needlestick injury to the fingers holding the needle cap. It would be better if a needle hub could be safely released without needing to cap the needle or handle the connection.
There are various fluid transfer procedures in the medical setting that may require a very secure connection between a fluid transfer tip (e.g., provided by a syringe) and a corresponding hub. The hub may be connected to a needle or catheter inserted into an artery, vein, cavity or organ of a patient. In the field of cardiology, angiography and angioplasty procedures may inject fluids (liquid and/or air) into narrow channels at high pressure. Manual syringes and manifold sets are used for percutaneous coronary interventions and coronary diagnostic procedures such as angiography. A cardiac angiographic kit typically may include a catheter hub for connection, a catheter body of chosen size, length and stiffness, and a tip with a single end-hole to eject fluids. The catheter body is inserted into the coronary vessels, ventricles and/or peripheral vasculature. A syringe may be connected to the catheter hub to inject contrast agents or saline at pressures ranging between 250 and 800 psi, and even up to 1000 or 1200 psi (84 bar). The catheter hub has an external thread to provide a standard Luer lock connection.
Luer lock connectors have become universal, not only for joining syringes to hubs, but also for connecting small-bore medical tubing and hoses for liquids and/or gases. Luer lock connections are commonly used for vascular IV lines but also find use in other medical treatment or diagnostic systems. Tubing and hoses may use a Luer lock connection for cuff inflation systems, feeding tubes, catheters, and hoses for vascular, enteral, respiratory, neuraxial and urethral/urinary systems.
The screw connection of a Luer lock hub is often considered necessary to withstand high pressures. However a syringe, hose, or other fluid transfer device must be rotated to connect, and disconnect, its Luer lock collar to/from the hub. This can take time and requires a two-handed operation. Furthermore, when a user grips the hub to unscrew the connection there is a risk of contamination, especially where the hub may include a needle that may carry blood on its shaft. It would improve the efficiency and workflow of medical procedures if a fluid transfer device could be disconnected from a Luer lock hub more easily.
There are various devices known in the art to assist in the removal of a Luer slip hub from a fluid transfer device. Many of these devices utilise a lever member capable of pushing the hub away from the tip of the fluid transfer device. In such embodiments the positioning of the lever member on the fluid transfer device can lead to accidental release of the hub, as the lever typically requires a small amount of force to be applied to it in order to remove the hub. This accidental release could be dangerous in instances where a needle is attached to the hub as this could result in a needlestick injury.
Arrangements for removing a Luer slip hub may also be used to remove a Luer-lock hub from a fluid transfer device. Some examples of this are taught in WO2014/020090. These fluid transfer devices typically may include a threaded collar attached to a lever member. Such a lever member is capable of moving the threaded collar away from the Luer-lock hub allowing it to be released. However The Applicant has now appreciated the potential for improvement of the arrangements taught in the above-mentioned application. In particular it has been recognised that in some circumstances there might be a tendency with such devices when screwing the Luer-lock hub to the device for the lever member to pull forward and away from the fluid transfer tip. This could cause the threaded collar to move away from the fluid transfer tip and so result in a poor connection between the hub and transfer tip which could lead to the loss of fluid during use of the fluid transfer device.